Patients with Hermansky-Pudlak syndrome have minor to moderate bleeding histories. We have examined platelet function, in particular platelet aggregation and release, in these patients and found they have deficient dense granule contents. We have measured plasma and platelet von Willebrand factor and plan to measure other platelet granule proteins. We will administer intravenous or intranasal desmopressin acetate to ascertain whether this therapy is effective in correcting patient's coagulation defects.